The currently popular bicycle constructions include what is known as a "coaster" bicycle, and a number of multiple-speed bicycles. The "coaster" bicycle is one in which a chain entrained around a sprocket driven by rotary pedals in turn rotates a smaller sprocket at the hub of the rear wheel, the smaller sprocket being adapted to drive the rear wheel when it rotates in the forwardly direction, and to brake the rear wheel when it is turned in the opposite direction. Several decades ago most popular bicycles were of the "coaster" type. Since that time, developments have included the three-speed bicycle, and then the five and ten-speed bicycles. Braking on all multiple speed bicycles is carried out by hand brakes usually mounted on the handle bars.
All of the foregoing bicycle constructions suffer from certain disadvantages. The first disadvantage relates to the fact that the pedals of the bicycle are mounted for rotary motion. Because of this pedal arrangement force cannot be efficiently applied to the pedals when they are in top or bottom dead center position. Force applied when a pedal is near the top of its swing gives only a small component in the rotary sense, the rest being axially directed along the arms supporting the pedal. Another shortcoming relates to the necessarily short arm on which pedals are normally mounted. The typical arm length is of the order of 61/2 to 7 inches. It is well known that a greater moment (torque) can be generated by using a given amount of force over a longer moment arm.
Another shortcoming of the conventional bicycle structures relates to the rather cumbersome way in which the gearing adjusts the pedal rotation for different speeds of the bicycle. All multiple-speed bicycles typically have one or more "gears" in which a given speed of pedal rotation will produce a relatively slow speed in the vehicle, though one in which greater power is available for forward motion. But bicycles also include one or more "high" gears, in which the same speed of pedal rotation produces a considerably faster forward motion in the bicycle. However, these multiple gearing systems, even that known as the ten speed system, are limited in terms of the maximum differential of the lowest gear and the highest gear. Furthermore, the changing of the gears itself is a tricky manoeuvre which normally wastes a certain period of time while the chain switches from one sprocket to another. During this switching manoeuvre forward driving force cannot be efficiently applied to the pedals. In many three-speed bicycles, the operator must actually cease pedalling to allow the gears to switch. The loss of this gear-switching time in terms of applying propulsive force to the pedals can make the difference between winning and losing a race.
In addition of the conventional structures described above which are available in the market place, certain other mechanisms are exemplified in prior patents. Some of these prior patents involve flywheels or similar energy-storing rotational members, but in many cases the mechanisms are hopelessly complicated and are such that much of the energy exerted by the operator will be lost in friction. One such prior art mechanism is illustrated in U.S. Pat. No. 1,784,419, issued Dec. 9, 1930 under A. Devito.
Another prior art structure incorporating a flywheel is that illustrated in U.S. Pat. No. 2,141,233, issued Dec. 27, 1938 to C. S. Alexander.
Yet another prior structure involving flywheels in exemplified in U.S. Pat. No. 4,037,854 issued July 26, 1977 to Eugene Large.
Mention has been made of these particular prior art patents for the purpose of explaining that the provision of a flywheel on a bicycle can be a mixed blessing, if the structure of the flywheel and the supporting elements are not correctly chosen. While on the one hand the presence of the flywheel allows the operator to store energy prior to "take off", many flywheel structures are necessarily quite heavy and certainly add extra weight to the bicycle which otherwise would not be present. It is well known, for example, that the most efficient storage of energy in a flywheel takes place when the flywheel has a relatively heavy rim, i.e. is one in which most of the weight is concentrated as far away from the axis of the flywheel as possible.
A particular disadvantage of at least some of the prior art patents listed above relates to the difficulty in properly shielding the flywheel from contact by the operator. Naturally, with the flywheel spinning at excessive rates of speed, it is quite important to keep skin or clothing free from contact with the flywheel. In the case of U.S. Pat. No. 4,037,854, several openly accessible wheels in addition to the riding wheels of the bicycle are provided, immediately adjacent to where operator is moving his legs. A similar situation arises in U.S. Pat. No. 2,141,233.